“Multipathing” enables a host computer to direct storage commands among multiple distinct paths to a given storage volume on a data storage system. The host computer typically selects among the paths to enhance performance, e.g., for load balancing purposes, to respond to failure of a particular path, and so on. An example of a multipathing driver which enables such operation is sold under the name PowerPath® by EMC Corporation of Hopkinton, Mass.
A conventional approach to detecting path errors involves occasional path testing by the multipathing driver of the host computer. Along these lines, the multipathing driver sends small computer system interface (SCSI) commands on demand or periodically to determine which paths are healthy.
For example, suppose that a storage processor of a data storage system has temporarily gone offline for a firmware upgrade. The multipathing driver running on the host computer may periodically test a target port of the data storage system using standard commands (e.g., SCSI inquiry and SCSI Mode Sense) to determine when the target port becomes available again.